I. Field of the Invention
This invention relates to devices for automatically stitching buttons onto articles of clothing.
II. Description of Related Art
A variety of devices are known in the apparel industry for automatically stitching buttons onto articles of clothing. Such devices have gained wide-spread acceptance and are considered essential to the mass production of most types of clothing having buttons.
For many applications, it is necessary only to sew the button flat against the clothing fabric. Such applications do not require much more than a basic sewing machine. However, certain types of clothing require a much more intricate button stitching process.
One such type of clothing is the traditional men's suit jacket. Buttons on suit jackets must first be sewn loosely to the jacket, after which the loose threads between the jacket fabric and the button are wrapped for strength.
In the case of buttons having holes through which the thread is passed in order to attach the button to the material, sewing and wrapping requires rotation of either the button or the needle during the stitching process, because the plane of the wrap is perpendicular to the plane of the attachment stitches. An example of a flat, four hole suit jacket button is shown in FIG. 7.
In addition, men's suits have traditionally required a higher quality of stitch, preferably approximating a hand-stitch. The appearance of the stitch on the inside of the jacket must be uniform. A tangle of threads, such as is produced by ordinary sewing machines, is unacceptable even on the inner side of the jacket.
A machine is commercially available which acceptably fulfills the tolerance requirements for men's suits. It operates by using a single needle and thread in a manner analogous to the needle and thread of a human seamster. The fabric is wrapped around a "tongue" in order to position the fabric in respect to the fabric, as shown in FIG. 2(a) and the needle is moved at right angles to the end of the tongue, penetrating the fabric to create a "blind" stitch which is not visible from the inside of the jacket.
The button is first located over the tongue in a plane perpendicular to the end of the tongue and parallel to the portion of the fabric to be stitched, which is wrapped over the end of the tongue. The single needle is driven into the fabric to anchor the attachment stitch, after which the button is rotated so that the holes in the button can be stitched, e.g., by moving the button under the control of a computer program so that the thread passes through selected holes therein according to a predetermined pattern.
In order to add a wrap stitch, the button is again rotated so that the plane of the button is substantially perpendicular to the principal plane of the tongue and parallel to the leading edge of the tongue (the right side of the tongue as shown in FIG. 2(a)), after which the threads leading from the button to the fabric are automatically wrapped and "lock" stitches are added to keep the thread from unraveling. In some cases, the wrapping step is omitted, especially in the case of suit jacket buttons which are intended to be decorative rather than functional.
All of the above steps may be easily initiated by an unskilled operator after selection of the desired stitch, the stitching steps being automatically performed under the control of a button stitcher control program.
However, intervention by a skilled operator is required in order to adjust the machine for different fabrics. It is crucial that the portion of the fabric to be stitched be precisely located in respect to the plane of movement of the needle, especially in the case of "blind" stiches. This is accomplished by adjusting the location of the end of the tongue nearest the needle, hereinafter referred to as the leading edge of the tongue.
Because of the way the fabric is folded over the leading edge of the tongue, the location of the tongue must be adjusted each time the fabric is changed. Such adjustment, using adjustment screws 11 as shown in FIG. 2(a), is both time-consuming and suffers from the disadvantage that a skilled operator is required to make the adjustment, whereas a rather lower level of skill is required simply to run the machine.
During stitching, the fabric must be held securely against the leading edge of the tongue, which means that the fabric should be pressed against both the top surface and the bottom surface of the tongue in order to hold it stationary against the leading edge and prevent excess loose fabric as, for example, in the case of a double-breasted suit, from interfering with movement of the stitching needle.
Although it is conventional to provide a "foot" for pressing the fabric against the top surface of the tongue, no means are currently available for securely pressing the fabric against the bottom of the tongue for maximum accuracy in holding the fabric against the leading edge of the tongue and out of the path of the stitching apparatus. Instead, the frame of the machine 8 serves to loosely support the fabric as shown in FIG. 2(a).
While the above-noted disadvantages, i.e., the need for adjustment when changing fabrics and the less than optimum holding of the fabric against the end of the tongue, have not prevented conventional button stitching machines from enjoying wide-spread popularity, the time and labor savings resulting from elimination of the necessity for adjustment for different fabric thicknesses, and the improved appearance that would result from better location of the fabric with respect to the leading edge of the tongue, could clearly produce significant commercial benefits. The present invention is a device which provides the above-noted benefits by an ingeniously simple attachment which can be retrofitted onto otherwise conventional button stitching machines.